If you can’t find any simple To Do apps or maybe you just don’t want to use any extra application to manage your tasks then Google has a solution for you, just head over to this Google Tasks link https://mail.google.com/tasks/ from your Android phone or tablet and you are ready to input your stuff. Every new task will automatically be saved to your gmail account, you can visit the same URL https://mail.google.com/tasks/ from your computer browser to access and edit the tasks. Alternatively you can use the below mentioned app.
Tip: Free app named Gtasks is also available which allows you to save tasks and lists locally on Android phone as well as provides an option to sync with Google Tasks. Download Gtasks for Android from Market.